This invention generally relates to heavy-duty off-road trucks and, more particularly, to a tailgate assembly for these trucks.
Certain working environments, such as coal mines, can require the use of rear dump off-road trucks to haul loads having different material densities. Since the optimal volumetric capacity for a truck body varies based on the density of the material to be hauled, such hauling operations can be difficult to conduct efficiently. For example, in the case of a coal mine, off-road trucks may be used to haul both coal, which has a relatively lighter density, and overburden (i.e. the earth otherwise removed in a coal mining operation), which has a relatively heavier density. If the heavier density overburden is hauled in trucks having bodies with a volumetric capacity designed to haul coal, the load can substantially exceed the gross vehicle weight rating of the truck if the body is filled to capacity. Conversely, if a truck having a relatively smaller body designed to haul overburden is used to haul coal, the load of lighter weight coal will not come close to reaching the maximum allowable payload capacity of the truck.
One way in which to address this issue is to provide a group of trucks, with relatively larger dump bodies, which are dedicated to hauling coal and a separate group of trucks, which have relatively smaller dump bodies, dedicated to hauling overburden. However, having trucks which are exclusively dedicated to hauling one particular material substantially reduces the overall truck fleet flexibility.
In order to permit off-road trucks used in working environments such as coal mines to be used in a more flexible manner, the dump bodies can be equipped with a selectively deployable tailgate assembly which can be used to adjust the volumetric capacity of the dump body. In particular, the dump body of the truck can be equipped with a tailgate assembly rotatable between a closed, in-service position at the rear of the truck body and an out-of-service position at the front of the truck body. With such a tailgate assembly, to increase the effective volumetric capacity of the truck body for hauling relatively lighter density material such as coal, the truck can be loaded with the tailgate in the closed, in-service position. Arranging the tailgate at the rear of the truck body increases the effective volumetric capacity of the truck body by preventing material from spilling out of the rear of the truck body. To lower the effective volumetric capacity of the truck body for hauling relatively heavier density material such as overburden, the truck can be loaded with the tailgate in the out-of-service position. When the tailgate is arranged in the out-of-service position at the front of the truck body, excess material loaded into the dump body will spill out of the open rear end of the body thereby minimizing the risk of overloading the truck body with the heavier overburden material.
Accordingly, such selectively deployable tailgate assemblies allow the effective volumetric capacity of a truck body to be selectively adjusted to permit a truck to efficiently haul loads of different volumes and material densities. As will be appreciated, the ability to selectively adjust the volumetric capacity of the dump body eliminates the need to provide differently sized trucks for hauling lighter density materials and heavier density materials.
One problem with such tailgate assemblies, however, is that when the tailgate is in the out-of-service position it can pose an obstacle to the loading operation. More specifically, when the tailgate is in the out-of-service position, the center rear portion of the tailgate, which extends between the two tailgate side beams, is oriented such that it extends upward and towards the rear end of the dump body overhanging the open top of the dump body. In this position, as material is being loaded into the dump body, the center rear portion of the tailgate is susceptible to being struck by the loading equipment or possibly by the actual material being loaded into the body. This can result in significant damage to the tailgate assembly necessitating costly repairs or even replacement. Moreover, the impact of a collision with the tailgate potentially could also damage the loading equipment.
Accordingly, in view of the foregoing, a general object of the present invention is to provide a dump body for a heavy-duty, off-road truck having a selectively deployable tailgate assembly which enables the truck to efficiently haul loads of varying volumes and material densities.
A more specific object of the present invention is to provide a dump body for a heavy-duty, off-road truck having a selectively deployable tailgate which minimizes potential interference with the loading of heavier density material into the dump body.
A related object of the invention is to provide a tailgate assembly as characterized above which minimizes the risk of damage to the tailgate assembly and dump body caused by possible over loading of heavier density material into the dump body/onto the rear dump off road truck.
Another object of the invention is to provide a tailgate assembly as characterized above which provides controlled and consistent movement of the tailgate assembly between in-service and out-of-service positions.
These and other features and advantages of the invention will be more readily apparent upon reading the following description of a preferred exemplary embodiment of the invention and upon reference to the accompanying drawings wherein: